DE19629432A1 - Aluminum salts of phosphinic acids - Google Patents

Abstract

The invention concerns aluminium salts of phosphinic acids or diphosphinic acids with alkyl and/or aryl substituents, obtained by heating an ester of the corresponding phosphinic acids or diphosphinic acids with aluminium hydroxide at a temperature of more than 150 DEG C under pressure in the presence of water. These salts are characterized by a particular crystal structure and are suitable as flame-proofing agents for plastics.

Description

The invention relates to aluminum salts of phosphinic acids, processes for their Production and their use as flame retardants.

Aluminum salts of phosphinic acids are valuable flame retardants for Molding compounds of polyester and polyamide. They are manufactured from the Phosphinic acids in aqueous solution with metal carbonates, metal hydroxides or metal oxides (EP-A2-0699708, internal name HOE 94 / F 256).

So far phosphinic acid esters have been saponified at 180 ° C. under pressure excess water only in the corresponding phosphinic acids good yields when converted from the gas phase of the autoclave formed alcohol is removed in a mixture with water (Houben-Weyl, Methods of Organic Chemistry 1982, Volume E2, page 142; DE-A1-27 45 982).

It has been found that the aluminum salts of phosphinic acids are under pressure from the corresponding esters with water and aluminum hydroxide in good Yields can be produced. Furthermore, it was found that the Aluminum salts of phosphinic acids or diphosphinic acids with alkyl and / or Aryl substituents at a temperature above 150 ° C under pressure in one new crystal form can be formed. These aluminum salts are called High temperature modification called. The at temperatures from 80 to 100 ° C. Manufactured, previously known aluminum salts are called Low temperature modification called.

The invention thus relates to aluminum salts of phosphinic acids or  Diphosphinic acids with alkyl and / or aryl substituents, obtainable by Heating an ester of the corresponding phosphinic acid or diphosphine acids with aluminum hydroxide at a temperature above 150 ° C under pressure in Presence of water.

Aluminum salts of phosphinic acids or diphosphinic acids with alkyl and / or Aryl substituents, obtainable by heating at a temperature above 150 ° C under pressure in the presence of water.

Alkyl substituents are preferably C₁-C₈-alkyl, especially C₁-C₄-alkyl, linear or branched, for example methyl, ethyl, n-propyl, iso-propyl, iso-butyl, n-butyl, n-hexyl or n-octyl. The preferred aryl substituent is Phenyl group.

The aluminum salts of the high temperature modification can also polymers of Be phosphinic acids or diphosphinic acids. The terms "phosphinic acid" and "Diphosphinic acid" accordingly include monomers, oligomers and polymers.

Another object of the invention is a method for producing Aluminum salts of phosphinic acids or diphosphinic acids, esters of corresponding phosphinic acids or diphosphinic acids with aluminum hydroxide be implemented under pressure at 150 to 350 ° C in the presence of water.

Another object of the invention is a method for producing Aluminum salts of phosphinic or diphosphinic acids High temperature modification, the corresponding aluminum salts in the Low temperature modification of a temperature in the range from 150 to 350 ° C exposed in the presence of water.

Suitable aluminum salts of phosphinic acids or diphosphinic acids are for example compounds according to formulas I or II

wherein
R¹, R² C₁-C₈-alkyl, preferably C₁-C₄-alkyl, linear or branched, e.g. B. methyl, ethyl, n-propyl, iso-butyl, n-butyl, n-hexyl, phenyl R³ C₁-C₁₀ alkylene, linear or branched, for. B. methylene, ethylene, n-propylene, iso-propylene, n-butylene, n-decycles, arylene, e.g. B. phenylene, naphthylene; Alkylarylene, e.g. B. methylphenylene, ethylphenylene, methylphenylene methyl, arylalkylene, e.g. B. phenylmethylene, phenylethylene. The aluminum salts according to formulas I or II are, for example, from phosphinic acid esters or diphosphinic acid diesters of the formulas III or IV

wherein R¹, R² and R³ have the meaning given above and R⁴ = C₁-C₈-alkyl, preferably C₄-C₆-alkyl can be produced. They will be advantageous Compounds according to formulas III or IV with water and aluminum hydroxide reacted under pressure at 150 to 350 ° C and at this temperature area heated for several hours, taking the appropriate aluminum salts  arise as a high-temperature modification.

Coming as raw materials for the production of the aluminum salts especially in question: methyl dimethylphosphinate, ethylmethyl ethyl phosphinate, isobutyl ethyl methylphosphinate, methyl n-butyl propylphosphinate, amyl isobutylmethylphosphinate, Isopropyl hexyl-methylphosphinate, n-butyl methyl-octylphosphinate, Methyl-phenylphosphinic acid n-butyl ester, diphenylphosphinic acid n-pentyl ester, Hexane-1,6-di- (methylphosphinic acid n-butyl ester), Benzene-1,4- (dimethylphosphinic acid isobutyl ester).

The process for producing the high temperature modification is described in one Variant carried out so that phosphinic acid esters with excess water and stoichiometric amounts of aluminum hydroxide under pressure to 150 to 350 ° C, preferably 180 to 250 ° C, advantageously with constant stirring, be heated. The required reaction times are generally between 4 and over 40 hours, especially at 50 to 70 hours. The Response times depend on the chain length of the ester group (for Example R₄ in formulas III and IV). The methyl esters saponify, for example faster than the butyl esters. After completion of the implementation, the ent standing crystals separated and dried. The reaction conditions like Temperature and reaction time can also be varied so that mixtures of low and high temperature modification can be obtained.

Aluminum salts of the high-temperature modification are changing Room temperature gradually into the low temperature modification, whereby however, the crystal costume of the high-temperature modification is preserved.

The high temperature modification consists of needle-shaped crystals that look fibrous. The crystals generally have a width in the range from about 0.2 to 1.5 µm, in particular 0.2 to 1 µm. The ratio of  The width to length of the crystals usually has a value of less than 0.2. The The ratio of the width to the length of the crystals is usually around 0.1 or underneath. The crystals usually form agglomerates that look like felt-like bales appearance. The agglomerates fall with a diameter in one size range from about 10 to 170 microns, with the majority of agglomerates with a diameter of about 20 microns.

The low temperature modification consists of cylindrical crystals, which in usually a width of more than 1.5 µm, typically 2 to 5 µm, identify. The ratio of the width to the length of the crystals is usually in Range from 0.6 to 2, typically at 2. The crystals also form Agglomerates that have a diameter of around 20 µm for the most part.

The high temperature modification of the aluminum salts is particularly suitable Way as a flame retardant or flame retardant for plastics, especially polyester or polyamide.

The aluminum salts of the high temperature modification have advantages for the Use as a flame retardant for plastics. Have investigations shown that the flame retardant effect of the salts of phosphinic acids in Plastic depends on the grain size of the salt and it is an optimal grain size there. The aluminum salts of the high temperature modification are created already in the favorable grain size. Grinding the aluminum salts is therefore for compounding not required, which is flaming for manufacture protected plastics means an economic advantage. Furthermore the finer structure of the aluminum salt allows a more homogeneous distribution of the flame retardant in the plastic. The fibrous structure of aluminum salt also leads to a strengthening of the plastic (fiber reinforcement). The finer structure leads to a larger surface of the grain and improves, for example, when using synergists like Nitrogen compounds their effect for flame protection.

example 1

308 g (1.75 mol) of n-butyl methyl n-propylphosphinate, 290 ml of water and 45.5 g (0.583 mol) of aluminum hydroxide are placed in a 1 liter autoclave filled and kept at 200 ° C with stirring for 50 hours. Then it is cooled and suctioned off, then dried. 214 g of aluminum salt are obtained Methyl n-propylphosphinic acid. This corresponds to a yield of 94% of theory. Th. The product does not melt up to 360 ° C. The product keeps the crystal costume a high temperature modification in (pseudomorphism).

If the product is manufactured according to EP-A2-0699708, it falls into the low-temperature modification (see also the attached tables the maxima of the X-ray diffraction patterns, Cu-Kα₁).

Example 2

264 g (1.5 mol) of n-butyl ethyl methylphosphinate, 250 ml of water and 39 g (0.5 mol) of aluminum hydroxide are in a 1 liter autoclave for 50 hours kept stirring at 200 ° C. Then it is cooled and suctioned off, then dried at 100 ° C in a vacuum drying cabinet. You get 157 g of aluminum salt of ethyl methylphosphinic acid with a Residual water content of 58 µm and an average grain size of 20.03 µm. This corresponds to a yield of 90% of theory. Th. The product melts up to 360 ° C Not. The product retains the crystal costume of a high temperature modification at (pseudomorphism).

If the product is manufactured in accordance with the patent specification EP-A2-0699708, so it occurs in the low temperature modification (see also the attached tables of the maxima of the X-ray diffraction patterns, Cu-Kα₁).

Example 3

213 g (1.2 mol) of ethyl methylphosphinate, 200 ml of water and 31.2 g (0.4 mol) of aluminum hydroxide are mixed in one at 190 to 220 ° C  1 liter autoclave held for 50 hours. Then it is suctioned off and dried. Man receives 123 g of aluminum salt of ethyl methylphosphinic acid. That corresponds to one Yield of 88.5% of theory Th. The product falls in the crystal costume of one High temperature modification (see example 1).

Table 1

X-ray diffraction diagram of aluminum methylpropylphosphinate (Debye-Scherrer beam path, Cu-Kα₁, transmission)

Table 2

X-ray diffraction pattern of aluminum ethyl methyl phosphinate (Cebye-Scherrer beam path, Cu-Kα₁, transmission)

Example 4

250 g of aluminum salt of ethyl methylphosphinic acid, produced at 90 ° C according to Example 1 in EP-A2-0699708 (low temperature modification), are in 250 g of water heated at 200 ° C for 50 hours. Then you leave Cool down to room temperature. The liquid is sucked off and the crystals dried. 230 g of aluminum salt of ethylmethylphosphinic acid are obtained in the crystal costume of the high temperature modification.

Example 5 (comparative example)

30 g of aluminum salt of ethyl methylphosphinic acid, produced at 90 ° C (Low temperature modification), 7 hours under nitrogen atmosphere stirred at 250 ° C. A conversion to the high temperature modification takes place practically not taking place.

Claims (9)

1. aluminum salt of phosphinic acids or diphosphinic acids with alkyl and / or Aryl substituents obtainable by heating an ester of the corresponding phosphinic acids or diphosphinic acids with aluminum hydroxide at a temperature above 150 ° C under pressure in the presence of water. 2. Aluminum salt according to claim 1, containing methyl, ethyl, propyl or Phenyl substituents. 3. aluminum salt according to claim 1 or 2, characterized in that the Aluminum salt in the form of crystals with a ratio of width to length less than 0.2. 4. aluminum-methylpropylphosphinate, characterized in that the Cu-Kα₁ X-ray diffraction pattern at 2 δ shows the following reflections:
8.35, 14.55, 20.05, 22.05, 23.40, 26.30, 28.95 and 32.45 °. 5. Aluminum-ethylpropylphosphinate, characterized in that the Cu-Kα₁ X-ray diffraction pattern at 2 δ shows the following reflections:
9.35, 18.95, 19.55, 25.45, 26.70, 27.15, 31.70, 32.60, 34.20 and 35.50 °. 6. Process for the preparation of aluminum salts of phosphinic acids or Diphosphinic acids, esters of the corresponding phosphinic acids or Diphosphinic acids with aluminum hydroxide under pressure at 150 to 350 ° C in Be implemented in the presence of water.   7. Process for the preparation of aluminum salts of phosphinic acids or Diphosphinic acids according to any one of claims 1 to 5, wherein at temperatures Aluminum salts produced below 100 ° C at temperatures in the range of 150 up to 350 ° C in the presence of water over a period of more than 40 Hours are heated. 8. Use of aluminum salt according to claims 1 to 5 as Flame retardants, preferably as flame retardants for plastics, especially as a flame retardant for polyester or polyamide. 9. Use of aluminum salt according to claim 8 in combination with one or more synergists, especially a nitrogen compound as Synergists.